How to create a new PTF using csv data from BgSaxo

Hi team, after reading a little bit around, I’m still not understanding how to start to create a my portfolio from the csv of my BgSaxo account (or other account, does not change)?
I’m problably missing the understanding logic, since I’m not starting now to invest, but would like to start from my position on 01 gen 2026.
Any help is higly appreciated
sandro